The user (Rik = rufn) reported this problem:
- Just before the problem appeared: Rik is not certain what he was doing but he may have disconnected a second hdd, he now only has one drive connected and had 2 earlier. He also installed the latest updates.
- Then: the system failed to boot and gave message "unknown filesystem grub ???"
- Attempt of GRUB repair: Rik ran Boot-Repair (from a Boot-Repair-Disk), and selected the recommended repair, which tried to reinstall GRUB via chroot into the installed Ubuntu (log: http://paste.ubuntu.com/1149152 ).

As we can see in the log:
- grub-install failed (MBR still points to sda6 when it should point to sda1)
- grub-install returned a 126 error code